What happens when a blower motor resistor is bad?

Without any power, the motor won’t run. As a result, the blower fan stays still and silent, and no air blows out of the vents. There are instances where a bad resistor will prevent the current from reaching the blower motor altogether. Resistors have it rough.

Can a broken motor switch stop a blower?

A broken blower motor switch can also stop the blower from changing to certain speed settings. If your blower motor cannot change to certain speeds, check both the resistor and the switch on your dashboard. The most common failure points are the resistor and the motor itself.

How is a step resistor used in a fan?

A voltmeter connected to both ends of a resistor while current is passing through it to a load will measure the amount of voltage being “dropped” by the resistor. Because lower voltage means lower current delivered to the fan, the stepped resistor circuit can be used to control fan speed.

How is the speed of the blower motor controlled?

On climate control systems without automatic temperature controls, the blower motor speeds are controlled by a switch wired to a stepped resistor that usually includes a thermal fuse.

When does a blower motor resistor need to be replaced?

If the resistance is out of specs, the resistor must be replaced. For example, in this photo we measured the resistance of this blower motor resistor. According to the service manual, it must be around 4-5 ohms. In our case the ohmmeter shows open circuit, which means the resistor has failed.

Where does the power transistor go in a blower motor?

The power transistor has 4 wires: two come from the climate control system control unit, one is the ground, one goes to the negative terminal of the blower motor. The service manual advises measuring the voltage at the blower motor, then if not OK, at the power transistor and so on.

What are the symptoms of a bad heater motor resistor?

Symptoms of a Bad or Failing Heater Blower Motor Resistor. 1 1. Blower motor stuck on one speed. A common symptom of a faulty blower motor resistor is a blower motor that is stuck on one setting. The blower 2 2. Blower motor does not work on certain settings. 3 3. No air from the vehicle’s vents.

What does the resistor on a heater do?

It is responsible for controlling the blower motor’s fan speed. When fan speed is changed via the knob on the instrument cluster, the blower motor resistor changes setting, which changes the speed of the blower motor.

Why is my furnace or AC blower not working?

Furnace or AC Blower Motor Not Starting or Working! Top 10 Reasons Why! – YouTube If playback doesn’t begin shortly, try restarting your device.

How to easily get your cars blower motor working again?

If playback doesn’t begin shortly, try restarting your device. My number one goal is to help you save money on your automotive repairs. Automotive Repair Videos for the do it your self-er to Master Mechanic or the flat rate mechanics (DIY) trying to trim a little time off there repairs. These videos are for everyone.

What happens if you have a bad blower motor?

The blower motor is the component responsible for pushing air through the vents of your vehicle’s heating and air conditioning systems. Without it, the AC system will not be able to circulate any heated or cooled air.

What happens if you lose the blower motor relay?

What causes a blower motor resistor to fail?

The most likely reasons for blower motor resistor failure can include: 1 Corrosion from long exposure to air and moisture. 2 Overheating—if a motor finds it harder to move because of jamming or worn bearings, it can raise the resistor’s temperatures to dangerous levels. 3 Normal wear due to time and use.

What causes a fuse to blow on a blower motor?

If the blower motor relay develops any sort of problem that hinders its ability to properly limit and distribute power, it may cause the blower motor fuse to blow. Any sort of electrical spikes or excessive current from a bad relay will blow the fuse and cut power in order to protect the system.

Where does the power go in a blower motor?

For each higher speed, power flows through one less resistor. Some car makers run blower motor power through the fan speed switch first, then through the blower motor resistor and then to the blower motor and ground. Other car makers reverse that and run power to the blower motor first and terminate ground at the blower fan speed switch.

What are the symptoms of a bad blower motor resistor?

Another common symptom of a faulty blower motor resistor is a a blower motor that does not function on certain settings. If the blower motor resistors’ internal components fail it may cause the blower motor to malfunction, or not function at all on one or more of the settings.

What happens when a heater motor resistor fails?

If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed. The heating and air conditioning systems may still function at one speed, however the resistor will have to be replaced in order for full functionality to be restored. 2. Blower motor does not work on certain settings

Why is my blower motor stuck on one speed?

Blower motor stuck on one speed A common symptom of a faulty blower motor resistor is a blower motor that is stuck on one setting. The blower motor resistor is the component directly responsible for controlling the blower motor fan speed. If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed.

Why is my blower motor not coming on?

With the back wire hooked up I ran a jumper directly to the battery pos and attached it the purple wire terminal on the motor. The motor did not come on. So either my motor is dead shorted or something has gummed up the brushes or they are worn out.

Where is the relay on a blower motor?

Correction assuming 97 is same (probably is)… Fan relay is as posted before on top of the duct work left of the resistors you can see both behind the glove box if you take it out. The purple wire comes from the relay/resistors according to fan speed selected.

How can I tell if my blower motor resistor is faulty?

Another symptom of a faulty blower motor resistor is no air from the vehicle’s vents at all. Power to the blower motor is fed through the blower motor resistor, so if it fails or has any issues power can be cut off to the motor.

What does the blower motor resistor do in a car?

The blower motor resistor is an electrical component that is a part of the vehicle’s heating and air conditioning system. It is responsible for controlling the blower motor’s fan speed. When fan speed is changed via the knob on the instrument cluster, the blower motor resistor changes setting, which changes the speed of the blower motor.

What does it mean if your blower motor is not working?

Average rating from 849 customers who received a AC is not working Inspection. The blower motor resistor is an electrical component that is a part of the vehicle’s heating and air conditioning system. It is responsible for controlling the blower motor’s fan speed.

What happens when a blower motor resistor is bad?